Modeling means that an object is depicted with a model. The aim of modeling is to provide a model that functions in the same way as the object it represents in the real word. How well this aim is achieved naturally depends on the properties of the modeling tool employed.
As data processing systems and computers have improved, modeling has become a computerized process. Parametric modeling systems, for example, have been devised for modeling complicated objects, such as buildings, which may consist of large numbers of different parts. These systems typically apply predefined elements that are provided with values in connection with the modeling. Examples of these elements include different parts, such as beams, columns, plates, different connections, details and macros and dimension lines used in drawings. A connection is usually made between two or more parts. A detail usually relates to one part and one point. A macro is more common than these two and can be used for creating spiral stairs and railings thereof, for example. In parametric modeling a beam, for example, is modelled by defining its starting and ending points and different parameters representing its physical properties. It is thus possible to model a beam in such a way that the form and size of the beam are no longer fixedly associated with the beam. In other words, the modelled object is not tied to the physical properties of the part it depicts, but the geometry of the object can be created, when needed, by using different parameters. The parameters of a beam, for example, may include location, material, type of cross-section and size. Since form and size are not fixedly associated with the object, the profile of the beam, for example, can be changed and thus the profiles of all beams modelled by copying one and the same beam can be updated very rapidly.
A change made to an object in the modeling program should also update the environment of the object. For example, the changing of a beam should change the connections between the beam and other beams, or, in other words, a connection should change according to the beams it is connected to. The updating of connections has been resolved by defining and storing different connections in software libraries from which the program selects the correct connections for particular beams and/or columns on the basis of specific rules. In other words, a predefined connection is defined as a complete piece of software that knows how the connection is to be produced. This solution involves problems caused by the fact that each connection requires a separate piece of software and by the memory space required by the libraries and the manageability thereof: different countries apply different standards to connections used between beams, and companies may apply standards of their own. Moreover, there are dozens of parameters associated with a beam that have an impact on a connection to be made between two beams, or between a beam and a column, a footing, or a slab. The library contains corresponding connections defined for columns and slabs, for example.
When a model has been created with this system using elements, such as connections, defined in advance in the system, and the model is to be changed by changing the thickness of a beam, for example, the system updates the connections, for example, to correspond to the changed situation. In other words, the functioning (behaviour) of objects created using predefined elements is programmed into the system and the objects are capable of adjusting themselves to changing situations as needed. This means that they comprise “intelligence”, i.e. they understand how connecting depends on the element to be connected and how a connection is produced depending on their parameters.
As indicated above, all alternatives that are possible and may be needed in modeling cannot be provided by predefined elements. It is therefore also possible that the user defines elements (known as compound elements) by using parts known as basic components in the modeling system. The user is not, however, capable of programming functioning or behaviour into an element he/she has defined. A problem with an object created using an element defined by the user is that the parameters and attributes of the object are associated with the physical properties specified for the element at the time of it was defined and the object does not take into account its environment or changes in the environment in any way. For example, although a connection defined by a user to the top of a column of a cross-sectional size of 300*300 can be copied to the top of a 400*400 column, the connection is not capable of updating its dimensions to correspond to the changed dimensions of the column. The user therefore has to define a new connection for a column top having a different cross-sectional surface. It takes more time to define a new connection than merely to copy one. Another alternative is that the user requests the system supplier to add the connection as a predefined connection to the software library and waits for the next system update. Correspondingly, if the column is reduced to a size 200*200, the outer dimensions of the connection remain unchanged, i.e. they are too big. In other words, objects created using elements defined by the user do not understand how a connection depends on the element to be connected and on the parameters of the object. This increases the risk of errors, and faulty elements may cause delay in construction works, for example, because when an object that is created by the user on the basis of a prototype changes, it must be kept in mind to manually update the connections and the parts to be connected according to the change and, correspondingly, changes made to the parts to be connected must be updated to the object concerned. For example, if the user has modelled a stiffener between the upper and lower flanges of a beam and then changes the height of the beam, the height of the stiffener does not change automatically. A corresponding problem appears in drawings generated on the basis of a model, because also the user can make dimension lines to drawings, the lines thus representing elements defined by the user. For example, the user may determine that a distance between two bolts is to be presented in the drawings. When the user then uses the model thus defined to make drawings and then moves one of the bolts, the dimension line is not updated to correspond to the new situation, although otherwise the model is correctly shown in the drawings, because the dimension line is fixedly associated with the physical position of the bolt in the drawings as it was at the time the dimension line was defined.